Impact of preoperative and postoperative membranous urethral length measured by 3 Tesla magnetic resonance imaging on urinary continence recovery after robotic-assisted radical prostatectomy

Abstract

Introduction: We sought to investigate the impact of preoperative and postoperative membranous urethral length (MUL) on urinary continence using 3 Tesla (3T) magnetic resonance imaging (MRI) after robotic-assisted radical prostatectomy (RARP).Methods: Between 2008 and 2013, 190 men with RARP underwent preoperative and postoperative MRI. Patients who received adjuvant radiotherapy or who were lost to followup were excluded, leaving 186 patients eligible for analysis. Preoperative MUL was estimated from the prostate apex to the penile bulb, while postoperative MUL was estimated from the bladder neck to penile bulb. Patients with no pads or protection were considered to have complete continence. Logistic regression analysis was used to identify predictors associated with urinary incontinence at six and 12 months.Results: Age was commonly associated with urinary incontinence at six and 12 months. In addition, diabetes mellitus (DM) was another factor associated with urinary incontinence at 12 months. When adjusting these variables, preoperative MUL ≤16 mm (95% confidence interval [CI] 1.01‒1.14; p=0.022), postoperative MUL ≤14 mm (95% CI 1.16‒9.80; p=0.025) and percent change of MUL >18% (95% CI 1.17‒7.23; p=0.021) were significantly associated with urinary incontinence at six months. However, at 12 months, preoperative MUL ≤13.5 mm (95% CI 1.85‒19.21; p=0.003) and postoperative MUL ≤13 mm (95% CI 1.24‒13.84; p=0.021) had impacts on urinary incontinence, but not percent change of MUL.Conclusions: Preoperative and postoperative MUL were significantly associated with urinary continence recovery after RARP. Therefore, efforts to preserve MUL are highly recommended during surgery for optimal continence outcomes after RARP.